1. Field of the Invention
The invention relates to an optoelectronic reading pen for scanning optically encoded information such as in the form of a bar or line code, as is known, for example, from the printed document "Hewlett-Packard Journal", January 1981, pages 3-10.
2. Discussion of Background
Optoelectronic reading pens, which can be used for scanning the optically encoded information, have been successfully used for a relatively long time for rapidly and faultlessly reading in large amounts of data such as are produced, for example, when articles are debited at the cash registers of large deparment stores having EDP-controlled store management.
In this arrangement, bar or line codes according to the UPC (Universal Product Code) or EAN (European Article Numbering) standard are normally used as optical codes.
Known optoelectronic reading pens essentially consist of an optoelectronic system which is accommodated in an elongated pen housing and is followed by a single - processing electronic system. The optoelectronic system comprises a light source, in most cases a light-emitting diode (LED), an optoelectronic sensor (photodiode or phototransistor) and optical devices (lenses or similar) which focus the light of the light source onto a small spot in the plane of scanning and similarly collect the light reflected from the information carrier and conduct it into the sensor.
The wavelength of the light used is either within the visible range (for example 655 nm) or in the infrared range (for example 820 nm). As described in the printed document initially mentioned, light source and sensor can be jointly integrated in one housing. In most cases, inserts of smooth and wear-resistant material are provided at the tip of the reading pen on the scanning side to ensure that the pen slides easily and has a long life.
The light source installed in the known reading pen has a comparatively high power consumption which leads to a current intake of typically 20-50 mA of the complete reading pen. A current intake of this magnitude is uncritical for as long as the reading pen is connected to a stationary mains-operated data processing device.
In contrast, problems arise when the reading pen is connected to small portable battery-operated data acquisition devices in which the power consumption of all system components plays a decisive role with respect to the usefulness and operability of the system.
To reduce the power consumption overall, a momentary-contact switch, with the aid of which the light source is switched on for a brief period only during the actual reading process, is provided in the known reading pen.
However, the momentary-contact switch control of the known reading pen does not lead to significant power saving when the reading pen is almost continuously being used. In addition, the momentary-contact switch makes operation of the reading pen more difficult.